Electric Power Steering Hands-On Detection via Resonance Filter
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Solution Overview
Problem
Conventional automatic steering systems are prone to noise interference from free vibration systems, affecting the accuracy of manual input detection, and require costly touch sensors, which decrease detection accuracy when gloves are worn or in certain environments.
Innovation Solution
An electric power steering apparatus that uses a torsion bar and a resonance filter to estimate the handle angle based on torsional angle and motor electrical angle signals, comparing actual and estimated angles to accurately judge hands-on or hands-off states without derivative calculations, thus reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional automatic steering systems use torque sensors and derivative calculations to detect manual input, then manual input detection capability is provided, but noise interference from free vibration systems reduces detection accuracy
Solution Approach 1:
The patent extracts and eliminates the problematic derivative calculation step from the conventional detection system. By using a resonance filter to directly process the torque sensor signal and obtain the manual input torque, the system removes the source of noise amplification while maintaining the detection capability.
Solution Approach 2:
The patent introduces a resonance filter as an intermediary component between the torque sensor and the manual input detection logic. This filter acts as a mediator that processes the raw torque signal to extract the manual input component without requiring derivative calculations, thereby reducing noise interference from free vibration systems.
2Measurement precision
If touch sensors are installed on the handle to detect manual input, then detection capability is provided, but cost increases and detection accuracy decreases when gloves are worn
Solution Approach 1:
The patent replaces the mechanical contact-based touch sensor system with a torque-based detection system. By measuring the torque applied to the steering handle through the torque sensor and processing it through a resonance filter, the system detects manual input without requiring direct physical contact sensors on the handle surface, thereby eliminating sensitivity to environmental factors like gloves and temperature.
3Ease of operation
If derivative calculations are performed on torque signals to detect manual input, then manual input detection is enabled, but noise from free vibration systems increases
Solution Approach 1:
The patent converts the harmful free vibration noise into a beneficial feature by using a resonance filter tuned to the natural frequency of the steering system. Instead of trying to eliminate all vibrations, the system exploits the resonant characteristics to amplify the manual input signal while filtering out other frequencies, thereby converting noise into a detection advantage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves accurate manual input judgment without increasing costs or being affected by noise from free vibration systems, improving detection accuracy and reliability.
Implementation Method 1
estimating a handle angle using a second order or higher resonance filter in harmony with a frequency response in hands-off
Implementation Method 2
A column shaft (a steering shaft or a handle shaft) 2 connected to a handle (a steering wheel) 1 is connected to steered wheels 8L and 8R through reduction gears 3... the steering shaft 2 is provided with a torque sensor 10 for detecting a steering torque Tr of the handle 1
Data Source
AI summary
An electric power steering apparatus that drives and controls a motor which applies an assist torque to a steering system of a vehicle and has a function switching between an assist mode and an automatic mode, including a torsion bar torsional angle calculating section to calculate a torsion bar torsional angle based on a torque information, an output-side column shaft relative angle generating section to output an output-side relative angle from an electrical angle signal of the motor, an actual handle angle calculating section to calculate an actual handle angle based on the torsion bar torsional angle and the output-side relative angle, a resonance filter to obtain an estimated handle angle in a hands-off state from the output-side relative angle, and a hands-on/off judging section to judge a hands-on state when a time that a deviation angle between the actual handle angle and the estimated handle angle is equal to or more than a predetermined angle is continued for the predetermined time or more.